The present invention relates to an electromagnetic contactor that has a movable iron piece shaped like a hinge, and in particular, to an iron core structure for an electromagnet with reduced manufacturing costs.
FIG. 11 is a cross sectional view for showing a structure of a conventional electromagnetic contactor. An iron core 3 formed of a main leg 5 and a yoke 4, and a coil 8 wound around a spool 6 for the main leg 5 are housed in a lower case 1 with the yoke 4 installed on the bottom 1A of the lower case 1. A laterally movable holder 10 is housed in an upper case 2, and is moved to the left by the force of a return spring 7 between the holder and the side wall of the upper case 2. The movable holder 10 includes movable contacts 11 via contact springs 13. Fixed contacts 12 are fixed to the upper case 2, and contacts 12A attached to the fixed contacts l2 face the contacts 11A attached to the movable contact 11 so that the contacts can be connected to or separated from each other. The movable and the fixed contacts 11 and 12 are connected to an external main circuit via terminals (not shown).
Furthermore, an engaging section 9A of a movable iron piece 9 is fitted in a fitting section 10A of the movable holder 10 in FIG. 11. The movable iron piece 9 extends from the inside of the lower case 1 to the inside of the upper case 2, and faces the left end surfaces of the main leg 5 and the yoke 4 to be rotatably supported on the bottom 1A of the lower case 1. The upper and lower cases 2, 1 are connected.
FIG. 12 is an exploded perspective view of FIG. 11. The iron core 3 is formed of the bar-like main leg 5 and the L-shaped yoke 4, and is arranged like a character U. The coil 8 is wound around the spool 6, and the main leg 5 is inserted into and fitted in a square opening 6A penetrating through the spool 6. The movable iron piece 9 is located in front of and to the left of the spool 6, and has at the top an engaging section 9A with a reduced width.
Returning to FIG. 11, when the coil 8 is energized, the movable iron piece 9 is attracted to the iron core 3 and rotates in the clockwise direction. Thus, the engaging section 9A of the movable iron piece 9 pushes the fitting section 10A of the movable holder 10 to the right, and the movable holder 10 moves to the right by overcoming the force of the return spring 7. Then, the contacts 11A contact the contacts 12A. Under this condition, the contact springs 13 push the movable contacts 11 toward the fixed contacts 12 to thereby provide good contact between the contacts 11A and 12A. On the other hand, when the coil 8 is deenergized, the attractive force of the iron core 3 is eliminated and the force of the return spring 7 overcomes to cause the movable holder 10 to move to the left while the movable iron piece 9 is rotated in the counterclockwise direction. Then, the contacts 11A and 12A are disconnected.
The contacts 11A and 12A in FIG. 11 are contacts (A contacts) that come into contact when the coil 8 is energized. Moreover, this electromagnetic contactor may include contacts which generally contact together, but are disconnected when the coil 8 is energized (B contacts).
Conventional apparatuses, such as those described above, however, require an expensive cutter for cutting a plate for the iron core, as well as a large number of processing steps. Namely, it is required that the iron core has sufficient attractive force, the main leg must have a large cross section, and the tip surface of the main leg must have a large pole surface. Thus, a thick iron plate is used as the material of the main leg 5 as shown in FIG. 12. With a thick iron plate, the cut surface sags when a general press machine operating at a normal speed is used, resulting in a reduced pole face area with inappropriate edge angle and flatness. Consequently, a special fast cutter is used to cut the main leg 5. Although the above problem is solved by cutting the material at high speed, the fast cutter is more expensive than a general press machine due to their better performance. Thus, a general press machine is recommended for this purpose.
In addition, in FIG. 12, since the tip surface 5A of the main leg 5 and the tip surface 4A of the yoke 4 constitute pole faces, these surfaces must be polished so as to be located in the same plane, and this requires a large number of processing steps.
Furthermore, the main leg 5 and the yoke 4 are joined together by means of resistance welding, and such welding requires a large number of processing steps.
It is an object of this invention to enable an iron core to be processed by using a press machine operating at a normal cutting speed, and to eliminate the need for welding and polishing steps in order to reduce the number of required processing steps.